From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Andrew Morton <akpm@linux-foundation.org>,
"James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>,
Helge Deller <deller@gmx.de>, Arnd Bergmann <arnd@arndb.de>,
Kees Cook <keescook@chromium.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>,
linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
linux-ia64@vger.kernel.org, linux-parisc@vger.kernel.org,
linux-arch@vger.kernel.org, linux-mm@kvack.org
Subject: [PATCH v3 10/12] lkdtm: Really write into kernel text in WRITE_KERN
Date: Sun, 17 Oct 2021 14:38:23 +0200 [thread overview]
Message-ID: <3ccab3dde1c8acf3125e82fb990896d7ef6e97b2.1634457599.git.christophe.leroy@csgroup.eu> (raw)
In-Reply-To: <cover.1634457599.git.christophe.leroy@csgroup.eu>
WRITE_KERN is supposed to overwrite some kernel text, namely
do_overwritten() function.
But at the time being it overwrites do_overwritten() function
descriptor, not function text.
Fix it by dereferencing the function descriptor to obtain
function text pointer.
And make do_overwritten() noinline so that it is really
do_overwritten() which is called by lkdtm_WRITE_KERN().
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
drivers/misc/lkdtm/perms.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
index 60b3b2fe929d..035fcca441f0 100644
--- a/drivers/misc/lkdtm/perms.c
+++ b/drivers/misc/lkdtm/perms.c
@@ -10,6 +10,7 @@
#include <linux/mman.h>
#include <linux/uaccess.h>
#include <asm/cacheflush.h>
+#include <asm/sections.h>
/* Whether or not to fill the target memory area with do_nothing(). */
#define CODE_WRITE true
@@ -37,7 +38,7 @@ static noinline void do_nothing(void)
}
/* Must immediately follow do_nothing for size calculuations to work out. */
-static void do_overwritten(void)
+static noinline void do_overwritten(void)
{
pr_info("do_overwritten wasn't overwritten!\n");
return;
@@ -113,8 +114,9 @@ void lkdtm_WRITE_KERN(void)
size_t size;
volatile unsigned char *ptr;
- size = (unsigned long)do_overwritten - (unsigned long)do_nothing;
- ptr = (unsigned char *)do_overwritten;
+ size = (unsigned long)dereference_function_descriptor(do_overwritten) -
+ (unsigned long)dereference_function_descriptor(do_nothing);
+ ptr = dereference_function_descriptor(do_overwritten);
pr_info("attempting bad %zu byte write at %px\n", size, ptr);
memcpy((void *)ptr, (unsigned char *)do_nothing, size);
--
2.31.1
next prev parent reply other threads:[~2021-10-17 12:39 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-17 12:38 [PATCH v3 00/12] Fix LKDTM for PPC64/IA64/PARISC Christophe Leroy
2021-10-17 12:38 ` [PATCH v3 01/12] powerpc: Move and rename func_descr_t Christophe Leroy
2021-10-18 5:58 ` Nicholas Piggin
2022-02-11 0:51 ` Kees Cook
2021-10-17 12:38 ` [PATCH v3 02/12] powerpc: Use 'struct func_desc' instead of 'struct ppc64_opd_entry' Christophe Leroy
2021-10-17 12:38 ` [PATCH v3 03/12] powerpc: Remove " Christophe Leroy
2021-10-17 12:38 ` [PATCH v3 04/12] powerpc: Prepare func_desc_t for refactorisation Christophe Leroy
2021-10-18 6:27 ` Nicholas Piggin
2021-10-18 7:08 ` Christophe Leroy
2022-02-11 0:54 ` Kees Cook
2022-02-11 7:39 ` Segher Boessenkool
2022-02-14 10:30 ` Christophe Leroy
2021-10-17 12:38 ` [PATCH v3 05/12] ia64: Rename 'ip' to 'addr' in 'struct fdesc' Christophe Leroy
2021-10-17 12:38 ` [PATCH v3 06/12] asm-generic: Define CONFIG_HAVE_FUNCTION_DESCRIPTORS Christophe Leroy
2021-10-17 12:38 ` [PATCH v3 07/12] asm-generic: Define 'func_desc_t' to commonly describe function descriptors Christophe Leroy
2021-10-18 6:29 ` Nicholas Piggin
2021-10-18 7:07 ` Christophe Leroy
2021-10-18 9:16 ` Nicholas Piggin
2021-10-17 12:38 ` [PATCH v3 08/12] asm-generic: Refactor dereference_[kernel]_function_descriptor() Christophe Leroy
2022-02-10 10:30 ` Michael Ellerman
2022-02-11 0:56 ` Kees Cook
2022-02-14 10:32 ` Christophe Leroy
2021-10-17 12:38 ` [PATCH v3 09/12] lkdtm: Force do_nothing() out of line Christophe Leroy
2021-10-17 12:38 ` Christophe Leroy [this message]
2021-10-17 12:38 ` [PATCH v3 11/12] lkdtm: Fix execute_[user]_location() Christophe Leroy
2021-12-17 11:49 ` Christophe Leroy
2021-12-17 17:12 ` Helge Deller
2022-01-19 19:28 ` Christophe Leroy
2022-01-19 22:00 ` Kees Cook
2022-02-11 1:01 ` Kees Cook
2021-10-17 12:38 ` [PATCH v3 12/12] lkdtm: Add a test for function descriptors protection Christophe Leroy
2022-02-11 1:09 ` Kees Cook
2022-02-14 10:34 ` Christophe Leroy
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